Determinants of plant establishment success in a multispecies introduction experiment with native and alien species

Supporting Information

SI Materials and Methods

S1. Detailed Information on the Selection of Study Species.

We used

a total of 93 herbaceous plant species from 15 different plant

families. Half of these species (45 species) are native to

Swit-zerland, and the other half (48 species) are alien to Switzerland.

To avoid introduction of problematic invasive species to our study

sites, we only used alien species that are commercially available as

ornamental garden plants and that are not considered

prob-lematic invaders. We chose ornamental alien species because

horticulture is the major introduction pathway for most invasive

plant species. Obviously, exclusion of known invasive species

limits the inferences that we can make about traits that allow

species to cross the later barriers in the invasion process (barriers

linked to reproduction and dispersal; ref. 1). Nevertheless, our

study provides insight into traits that allow species to cross the

first barriers (abiotic and biotic environmental barriers at the site

of introduction).

To be able to correct for taxonomy, we wanted most families to

be represented by both native and alien plant species. From the

full list of seed-plant families that are native to Switzerland, we

excluded monocots and carnivorous plant families, because the

majority of invasive species in Europe is represented by other

plant taxa (2). Because we focused on invasions in grasslands, we

further excluded families mainly found in swampy or aquatic

habitats as well as parasitic and woody families. This process

resulted in a list of 55 plant families. For those, we searched in

seed catalogs of commercial seed suppliers for confamilial native

and alien species that were readily available in large quantities.

We excluded species that are not winter hard and further

re-stricted our selection to species only found in open habitats (i.e.,

we excluded species restricted to forests). To be able to

gener-alize our results across life histories, we chose both perennial and

nonperennial (annual and biennial) species. Our

final set of

study species thus consisted of 93 plant species and was, apart

from the above-mentioned restrictions, selected randomly. We

obtained seeds of the 93 study species from commercial seed

suppliers (UFA Samen, Wyss Samen und Pflanzen,

Samen-Steffen, B and T World Seeds, and Thompson & Morgan).

S2. Pseudo R2_{as a Goodness-of-Fit Measure.}

_{In generalized linear}

mixed-effects models (GLMMs), it is not possible to obtain an

R

as a goodness-of-fit measure. We therefore calculated pseudo-R

values, based on the residual deviance of our

final model and the

one of a null model, using the formula in Zuur et al. (3). The use

of pseudo-R

_{values as goodness-of-fit measure is not without}

controversy (4), and for mixed models the question of whether or

not the null model should contain the random factors remains

open. Therefore, we calculated pseudo-R

_{values using both types}

of null models.

1. Richardson, et al. (2000) Naturalization and invasion of alien plants: Concepts and

definitions. Divers Distrib 6(2):93–107.

2. Lambdon PW, et al. (2008) Alienflora of Europe: Species diversity, temporal trends,

geographical patterns and research needs. Preslia 80:101–149.

3. Zuur A, Ieno EN, Saveliev AA, Smith GM (2009) Mixed Effects Models and Extensions in Ecology with R (Springer, New York).

4. Mc Cullagh P, Nelder JA (2000) Generalized Linear Models (Chapman & Hall, London).



Published in "3URFHHGLQJVRIWKH1DWLRQDO$FDGHP\RI6FLHQFHV

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which should be cited to refer to this work.

Fig. S1. Estimates± SEM of the effects of species characteristics on establishment for the first two censuses only and separately for native and alien species. Estimates indicate how much the logit of the establishment probability increases when moving from one factor level to the other (e.g., from no soil disturbance to soil disturbance) or, in the case of covariables (e.g., seed mass), when increasing the covariable with one unit (i.e., with one SD). Effect of all plotted traits differed for native and alien species. Effects of several traits also changed between seasons or between disturbed and nondisturbed sites (significant inter-actions with status, season, or soil disturbance; see seed mass in Table S4).



Table S1. Number of established plant species and individual plants in thefield for each of the six censuses, separately for native and alien plant species

Time Native Alien No. of species No. of plants No. of species No. of plants First spring 16 20,906 34 11,159 First summer 24 (1) 1,151 (1) 24 (3) 3,465 (50) Second spring 11 411 8 181 Second summer 16 (5) 466 (18) 3 16 Third spring 12 (3) 316 (32) 2 13 Third summer 12 (7) 246 (86) 2 5

The numbers offlowering species and flowering plants are given in parentheses. Of the 93 plant species (45 natives and 48 aliens) introduced into the 16 sites, 64 species (28 natives and 36 aliens) were found at least once during the 3 y of observation, and 12 of them (9 natives and 3 aliens)flowered.



Table S2. Estimates and SEs from a GLMM with the presence–absence of a species in a subplot as response variable, combined for all six censuses

Fixed effects Estimate± SEM Likelihood ratioχ2 _{P value}

Soil disturbance 0.075± 0.360 0.044 0.834 Propagule pressure 2.713± 0.221 40.952 <0.0001 Standing biomass −1.153 ± 0.273 15.175 <0.0001 Year −2.745 ± 0.459 12.423 0.0004 Season −1.205 ± 0.743 2.231 0.135 Status 2.544± 0.637 14.338 0.0002

Thousand seed mass 1.998± 0.316 32.189 <0.0001

Germination percentage greenhouse 0.062± 0.507 0.013 0.908

Relative growth rate 0.182± 0.272 0.422 0.516

Response to competition −0.754 ± 0.258 7.470 0.006

Herbivore resistance 0.089± 0.237 0.130 0.718

Shoot–root ratio 0.298± 0.233 1.573 0.210

Response to shading 0.127± 0.275 0.212 0.645

Life history− perennial 0.290± 0.560 0.226 0.635

Year× season — — —

Soil disturbance× propagule pressure — — —

Soil disturbance× status — — —

Soil disturbance× thousand seed mass — — —

Soil disturbance× germination percentage greenhouse −0.587 ± 0.305 3.694 0.055

Soil disturbance× relative growth rate 0.523± 0.203 6.558 0.010

Soil disturbance× response to competition — — —

Soil disturbance× herbivore resistance — — —

Soil disturbance× shoot–root ratio — — —

Soil disturbance× response to shading −0.148 ± 0.217 0.451 0.502

Soil disturbance× life history − perennial 1.604± 0.414 14.900 0.0001

Year× status 2.449± 0.387 51.770 <0.0001

Year× soil disturbance* 1.049± 0.295 13.790 0.0002

Year× propagule pressure −0.658 ± 0.188 10.179 0.001

Year× standing biomass −0.448 ± 0.257 3.419 0.064

Year× thousand seed mass — — —

Year× germination percentage greenhouse — — —

Year× relative growth rate — — —

Year× response to competition 0.333± 0.158 4.485 0.034

Year× herbivore resistance 0.784± 0.177 24.252 <0.0001

Year× shoot–root ratio — — —

Year× response to shading −0.505 ± 0.140 13.110 0.0003

Year× life history − perennial 1.374± 0.485 10.070 0.002

Season× status 2.037± 0.376 29.082 <0.0001

Season× soil disturbance* 1.063± 0.314 11.334 0.0008

Season× propagule pressure — — —

Season× standing biomass — — —

Season× thousand seed mass — — —

Season× germination percentage greenhouse — — —

Season× relative growth rate −0.991 ± 0.203 23.551 <0.0001

Season× response to competition — — —

Season× herbivore resistance 0.814± 0.174 22.498 <0.0001

Season× shoot–root ratio −0.553 ± 0.179 9.298 0.002

Season× response to shading — — —

Season× life history − perennial — — —

Year× soil disturbance × propagule pressure — — —

Season× soil disturbance × propagule pressure — — —

Year× season × soil disturbance — — —

Year× season × propagule pressure — — —

Year× season × standing biomass — — —

Year× season × status — — —

Year× season × thousand seed mass — — —

Year× season × germination percentage greenhouse — — —

Year× season × relative growth rate — — —

Year× season × response to competition — — —

Year× season × herbivore resistance — — —

Year× season × shoot–root ratio — — —

Year× season × response to shading — — —



Table S2. Cont.

Fixed effects Estimate± SEM Likelihood ratioχ2 _{P value}

Year× season × life history − perennial — — —

Soil disturbance× year × status — — —

Soil disturbance× year × thousand seed mass — — —

Soil disturbance× year × germination percentage greenhouse — — —

Soil disturbance× year × relative growth rate — — —

Soil disturbance× year × response to competition — — —

Soil disturbance× year × herbivore resistance — — —

Soil disturbance× year × shoot–root ratio — — —

Soil disturbance× year × response to shading −0.692 ± 0.259 7.595 0.006 Soil disturbance× year × life history − perennial 2.578± 1.368 6.683 0.009

Soil disturbance× season × status — — —

Soil disturbance× season × thousand seed mass — — —

Soil disturbance× season × germination percentage greenhouse — — —

Soil disturbance× season × relative growth rate — — —

Soil disturbance× season × response to competition — — —

Soil disturbance× season × herbivore resistance — — —

Soil disturbance× season × shoot–root ratio — — —

Soil disturbance× season × response to shading — — —

Soil disturbance× season × life history − perennial — — —

Soil disturbance× year × season × propagule pressure — — —

Soil disturbance× year × season × status — — —

Soil disturbance× year × season × thousand seed mass — — —

Soil disturbance× year × season × germination percentage greenhouse — — —

Soil disturbance× year × season × relative growth rate — — —

Soil disturbance× year × season × response to competition — — —

Soil disturbance× year × season × herbivore resistance — — —

Soil disturbance× year × season × shoot–root ratio — — —

Soil disturbance× year × season × response to shading — — —

Soil disturbance× year × season × life history − perennial — — —

Random effects Variance

Site 0.237

Family 0.020

Family/species 2.149

Subplot 1.453

Time (categorical) 0.237

To obtain estimates, we started with a full model including the factors listed below and reduced thefixed terms by stepwise deletion of nonsignificant terms and comparing the resulting model to the previous one using log likelihood-ratio tests. This process resulted in a minimal model containing only factors that were significant as main effects and/or in interactions with other factors. We kept all random factors in the model and present their variance. Estimates and significances of three-way interactions were derived by comparing the model without the factor of interest to the full model using log likelihood-ratio tests. To obtain estimates and significances of two-way interactions, we excluded all three-way interactions and compared this model with models missing the factors of interest. To obtain estimates and significances of main terms we excluded all higher-level interactions and compared this model with models missing the factors of interest.

*The estimates of soil disturbance× year and soil disturbance × season, which were measured at the field level, are based on models from which we excluded all soil disturbance× species traits interactions.



Table S3. Estimates and SEs from a linear mixed model using the log-transformed number of established plants per subplot as the response variable, for each of the six censuses separately

Fixed effects First spring First summer Second spring Second summer Third spring Third summer

Soil disturbance −0.148 ± 0.289

Propagule pressure (log) 1.448± 0.153*** 1.057 ± 0.237*** 1.034± 0.226*** 1.050 ± 0.278** 1.192 ± 0.385*

Standing biomass −0.608 ± 0.237**

Status− native −5.199 ± 2.40**

− soil disturbance −0.358 ± 0.236 — — — —

+ soil disturbance 0.275± 0.242** — — — —

Life history− perennial — — —

− soil disturbance — — — —

+ soil disturbance — — — —

Thousand seed mass (log) 0.399± 0.102*** 0.401 ± 0.156** −1.024 ± 1.41 −1.222 ± 0.495**

− soil disturbance — — — —

+ soil disturbance — — — —

Germination percentage greenhouse −2.954 ± 1.063

− soil disturbance — — — —

+ soil disturbance — — — —

Relative growth rate 0.234± 0.141(_*) _{−0.3407 ± 1.398** −0.745 ± 0.278* −2.540 ± 0.967**}

− soil disturbance −0.316 ± 0.129(_*) _{— — — —} + soil disturbance −0.107 ± 0.138(_*) _{— — — —} Response to competition −0.309 ± 0.471 −0.316 ± 0.184(_*)_{−0.662 ± 0.238**} − soil disturbance — — — — + soil disturbance — — — — Herbivore resistance 0.367± 0.129** 1.309± 0.777(_*) _{2.504± 1.228**} − soil disturbance — — — — + soil disturbance — — — —

Shoot–root ratio −2.635 ± 1.353*

− soil disturbance −0.099 ± 0.11 — — — —

+ soil disturbance 0.398± 0.125** — — — —

Response to shading −0.36 ± 0.140** 0.761± 0.642 — —

− soil disturbance — — — —

+ soil disturbance — — — —

Random effects Variance

Site 0.215 0.011 <0.0001 <0.0001 <0.0001 0.266

Family 0.823 0.911 <0.0001 <0.0001 <0.0001 <0.0001

Family/species 0.228 0.197 0.516 0.015 <0.0001 <0.0001

Because of low numbers of observations in the censuses of the second spring, second summer, third spring and third summer, the models did not converge, and we had to exclude all interaction terms with soil disturbance, and, except for the census second spring, as well the factor life history and hypocotyl elongation in response to shading to achieve convergence (indicated by−). We kept random factors in the model and present their variance. If there was a significant interaction between a species characteristic and disturbance, we present separate estimates for the species characteristic in undisturbed and disturbed sites. Significance level of the estimates for a species characteristic in the absence of disturbance refers to whether the estimate differed from zero. Significance level of the estimates for a species characteristic in the presence of disturbance refers to whether the estimate differed from the one in the absence of disturbance. Significance levels: (*)P < 0.1; *P < 0.05; **P < 0.01; ***P < 0.001.



Table S4. Estimates and SEs from a GLMM with the presence–absence of a species in a subplot as response variable, combined for the first two censuses only

Fixed effects Estimates± SEM Likelihood ratioχ2 _{P value}

Soil disturbance −0.09 ± 0.334 0.077 0.781

Propagule pressure 2.433± 0.205 37.463 <0.0001

Standing biomass −0.95 ± 0.245 12.548 0.0004

Season −2.45 ± 0.182 10.032 0.002

Status 1.702± 0.536 9.414 0.002

Thousand seed mass 1.844± 0.277 33.109 <0.0001

Germination percentage greenhouse 0.142± 0.446 0.092 0.762

Relative growth rate 0.035± 0.237 0.021 0.885

Response to competition −0.64 ± 0.228 35.397 <0.0001

Herbivore resistance 0.084± 0.207 143.729 <0.0001

Shoot–root ratio 0.205± 0.204 0.974 0.324

Response to shading 0.169± 0.239 76.984 <0.0001

Life history− perennial — — —

Soil disturbance× propagule pressure — — —

Soil disturbance× standing biomass 0.277± 0.721 0.164 0.685

Soil disturbance× status 0.533± 0.498 1.120 0.290

Soil disturbance× thousand seed mass −0.01 ± 0.283 0.001 0.981

Soil disturbance× germination percentage greenhouse −0.13 ± 0.390 0.108 0.742

Soil disturbance× relative growth rate — — —

Soil disturbance× response to competition — — —

Soil disturbance× herbivore resistance — — —

Soil disturbance× shoot–root ratio — — —

Soil disturbance× response to shading — — —

Soil disturbance× life history − perennial — — —

Status× propagule pressure 0.572± 0.363 2.953 0.086

Status× standing biomass — — —

Status× thousand seed mass 1.096± 0.903 1.428 0.232

Status× germination percentage greenhouse — — —

Status× relative growth rate 1.851± 0.670 7.104 0.008

Status× response to competition 1.398± 0.579 5.452 0.020

Status× herbivore resistance — — —

Status× shoot–root ratio 0.412± 0.946 0.188 0.665

Status× response to shading — — —

Status× life history − perennial — — —

Season× soil disturbance* 0.735± 0.363 4.014 0.045

Season× propagule pressure 0.060± 0.325 0.037 0.847

Season× standing biomass −0.190 ± 0.337 0.315 0.574

Season× status 1.295± 0.562 5.369 0.020

Season× thousand seed mass 0.038± 0.309 0.016 0.901

Season× germination percentage greenhouse −0.16 ± 0.412 0.141 0.707

Season× relative growth rate −0.84 ± 0.225 11.391 0.0002

Season× response to competition — — —

Season× herbivore resistance 0.855± 0.205 11.831 <0.0001

Season× shoot–root ratio −0.44 ± 0.188 5.482 0.019

Season× response to shading — — —

Season× life history − perennial — — —

Soil disturbance× season × propagule pressure — — —

Soil disturbance× season × standing biomass 32.22± 11.18 10.660 0.001

Soil disturbance× season × status −8.675 ± 4.476 34.630 <0.0001

Soil disturbance× season × thousand seed mass −7.104 ± 3.610 111.180 <0.0001

Soil disturbance× season × germination percentage greenhouse −11.13 ± 4.127 110.590 <0.0001

Soil disturbance× season × relative growth rate — — —

Soil disturbance× season × response to competition — — —

Soil disturbance× season × herbivore resistance — — —

Soil disturbance× season × shoot–root ratio — — —

Soil disturbance× season × response to shading — — —

Soil disturbance× season × life history − perennial — — —

Status× season × standing biomass — — —

Status× season × thousand seed mass −10.327 ± 4.349 120.200 <0.0001

Status× season × germination percentage greenhouse — — —

Status× season × relative growth rate — — —

Status× season × response to competition — — —



Table S4. Cont.

Fixed effects Estimates± SEM Likelihood ratioχ2 _{P value}

Status× season × herbivore resistance — — —

Status× season × shoot–root ratio −14.172 ± 5.349 117.840 <0.0001

Status× season × response to shading — — —

Status× season × life history − perennial — — —

Soil disturbance× status × propagule pressure — — —

Soil disturbance× status × standing biomass — — —

Soil disturbance× status × thousand seed mass — — —

Soil disturbance× status × germination percentage greenhouse — — —

Soil disturbance× status × relative growth rate — — —

Soil disturbance× status × response to competition — — —

Soil disturbance× status × herbivore resistance — — —

Soil disturbance× status × shoot–root ratio — — —

Soil disturbance× status × response to shading — — —

Soil disturbance× status × life history − perennial — — —

Status× season × soil disturbance × propagule pressure — — —

Status× season × soil disturbance × standing biomass — — —

Status× season × soil disturbance × thousand seed mass — — —

Status× season × soil disturbance × germination percentage greenhouse — — —

Status× season × soil disturbance × relative growth rate — — —

Status× season × soil disturbance × response to competition — — —

Status v season× soil disturbance × herbivore resistance — — —

Status× season × soil disturbance × shoot–root ratio — — —

Status× season × soil disturbance × response to shading — — —

Status× season × soil disturbance × life history − perennial — — —

Random effects Variance

Site 4.223

Family 0.003

Family/species 0.306

Subplot 0.023

Time (categorical) <0.0001

To obtain estimates, we started with a full model including the factors listed below and reduced thefixed terms by stepwise deletion of nonsignificant terms and comparing the resulting model to the previous one using log likelihood-ratio tests. This process resulted in a minimal model containing only factors that were significant as main effects and/or in interactions with other factors. We kept all random factors in the model and present their variance. Estimates and significances of three-way interactions were derived by comparing the model without the factor of interest to the full model using log likelihood-ratio tests. To obtain estimates and significances of two-way interactions, we excluded all three-way interactions and compared this model with models missing the factors of interest. To obtain estimates and significances of main terms we excluded all higher levels interactions and compared this model with models missing the factors of interest.

*The estimates of soil disturbance× season, which were measured at the field level, are based on models from which we excluded all soil disturbance × species traits interactions.



Table S5. List of the 93 plant species used in the study and overview of the species present in each of thefive experiments

Family Species name Life history Status Field

Seed mass and germination

percentage

Response to shading

Shoot–root ratio and relative growth rate Response to competition Herbivore resistance

Asteraceae Achilleafilipendulina p A + + + + + +

Calendula officinalis np A + + + + + + Helianthus annuus np A + + + + + + Senecio bicolor p A + + + + + + Zinnia angustifolia np A + + + + + + Chrysanthemum carinatum np A + + + Aster bellidiastrum p N + + + Cichorium intybus p N + + + + + + Erigeron acer p N + + + Leucanthemum vulgare p N + + + + + + Senecio ovatus p N + + + +

Boraginaceae Anchusa capensis p A + + + + + +

Cynoglossum amabile p A + + + + + + Anchusa arvensis p N + + + + + Anchusa officinalis p N + + + + Borago officinalis np N + + + + Cynoglossum officinalis p N + + + + + Echium vulgare p N + + + + + +

Brassicaceae Alyssum saxatile p A + + + + +

Arabis caucasia p A + + + + + + Bunias orientalis p A + + + Iberis sempervirens p A + + + + + + Lobularia maritima p A + + + + + + Alyssum alyssoides p N + + Arabis hirsuta p N + + + Cardamine pratensis p N + + Iberis amara p N + +

Campanulaceae Campanula pyramidalis p A + + + + + +

Lobelia erinus np A + + + + + +

Platycodon grandiflorus p A + + + + + +

Symphyandra armena p A + + + + + Campanula barbata p N + + Campanula rapunculus p N + + + Campanula rotundifolia p N + + + + Legousia speculum-veneris p N + + + Phyteuma orbiculare p N + +

Caryophyllaceae Dianthus caryophyllus p A + + + + + +

Gypsophila elegans np A + + + + + + Lychnis chalcedonica p A + + + + + + Silene coeli-rosa np A + + + + + + Dianthus armeria p N + + + + + + Lychnisflos-cuculi p N + + + Saponaria officinalis p N + +

Convolvulaceae Convolvulos tricolor p A + + + + + +

Ipomoea tricolor np A + + + + + +

Calystegia sepium p N + + +

Convolvulus arvensis p N + + + + + +

Dipsacaceae Knautia arvensis p N + + + + +

Scabiosa columbaria p N + + +

Fabaceae Lathyrus odoratus np A + + + + + +

Lupinus hartwegii np A + + + + + +

Phaseolus coccineus np A + + + + +

Medicago lupulina np N + +

Lamiaceae Salvia argentea p A + + + + + +

Salvia farinacea p A + + + + + + Salvia lyrata p A + + + + + + Thymus× citriodorus p A + + + + + + Ajuga reptans p N + + + Galeopsis angustifolia np N + + Salvia glutinosa p N + + 

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Table S5. Cont.

Family Species name Life history Status Field

Seed mass and germination

percentage

Response to shading

Shoot–root ratio and relative growth rate Response to competition Herbivore resistance Thymus pulegioides p N + + + + +

Malvaceae Althaea rosea p A + + + + + +

Anoda cristata np A + + + + + + Hibiscus trionum np A + + + + + Lavatera trimestris np A + + + + + + Malva alcea p N + + + + + + Malva moschata p N + + + + + + Malva neglecta p N + + + + + +

Onagraceae Clarkia amoena np A + + + + + +

Oenothera glazioviana p A + + + + + +

Oenothera macrocarpa p A + + + + + +

Circaea lutetiana p N + +

Epilobium dodonai p N + +

Papaveraceae Eschscholtzia californica p A + + + +

Meconopsis betonicifolia p A + + Meconopsis cambrica p A + + Papaver communatum np A + + + + + Papaver orientale p A + + + + Chelidonium majus p N + + Papaver dubium np N + + + + Papaver rhoeas np N + + + + +

Polemoniaceae Phlox drummondii np A + + + + + +

Polemonium caeruleum p N + + + + + +

Ranunculaceae Aquilegia viridiflora p A + + + + + +

Clematis mandshurica p A + + + +

Aquilegia vulgaris p N + + + +

Clematis vitalba p N + +

Nigella arvensis np N + + + + + +

Solanaceae Datura stramonium np A + + +

Nicotiana sylvestris np A + + + + + +

Physalis peruviana p A + + + + + +

Solanum nigrum np N + + + +

Solanum dulcamara p N + +

Because of differences in germination, we could not assess each trait for all 93 plant species. We had complete data for 45 species. np, nonperennial (annual or biannual); p, perennial; A, alien species; N, native species.



Table S6. Characteristics of the experimental grassland sites

Site name Latitude Longitude

Propagule pressure Soil disturbance Species richness Productivity, g/m2 Mean Ellenberg indicator value to nutrients Kräiligen N47° 08′ 30″ E7° 31′ 20″ 1 No 22 392.8 5.9 Worblaufen N46° 59′ 33.86″ E7° 28′ 43.73″ 1 No 24 362.8 5.9

Albligen N46° 51′ 16.58″ E7° 19′ 14.28″ 1 Yes 17 775.0 6.6

Bützberg N47° 12′ 19″ E7° 43′ 24.41″ 1 Yes 26 264.6 6.6

Bützberg N47° 12′ 44.15″ E7° 45′ 33.31″ 5 No 21 556.6 6.1

Rüderswil N46° 59′ 02.51″ E7° 42′ 59.73″ 5 No 32 384.5 5.5

Büren a. d. Aare N47° 08′ 35″ E7° 23′ 22″ 5 Yes 16 648.7 6.3

Heimiswil N47° 03′ 58″ E7° 39′ 58″ 5 Yes 30 404.4 6.7

Mülchi N47° 06′ 03″ E7° 28′ 13″ 50 No 29 369.8 6.4

Signau N46° 56′ 28″ E7° 45′ 35″ 50 No 43 357.3 6.1

Hindelbank N47° 02′ 25″ E7° 33′ 25″ 50 Yes 34 568.6 6.7

Wiedlisbach N47° 14′ 48″ E7° 39′ 34″ 50 Yes 34 266.9 6.2

Heimiswil N47° 03′ 38″ E7° 38′ 43″ 500 No 51 307.6 4.8

Walliswil N47° 14′ 51″ E7° 49′ 30″ 500 No 42 320.8 5.5

Bätterkinden N47° 07′ 34″ E7° 32′ 17″ 500 Yes 25 215.9 5.6

Rüderswil N46° 59′ 31.81″ E7° 42′ 49.31″ 500 Yes 28 374.1 6.5

We calculated mean indicator values to nutrients per site according to Ellenberg et al. (1).

1. Ellenberg H, Weber HE, Düll R, Wirth V, Werner W (2001) Zeigerwerte von Pflanzen in Mitteleuropa. Scripta Geobotanica 18:1–262.

Table S7. Pearson’s correlation coefficients between the measured species traits Seed mass Germination percentage Relative growth rate Shoot–root ratio Response to competition Herbivore resistance Germination percentage −0.512

Relative growth rate 0.008 0.209

Shoot–root ratio −0.092 0.157 −0.307

Response to competition

−0.060 −0.258 0.086 −0.019

Herbivore resistance −0.091 0.194 −0.091 0.199 −0.055

Response to shading 0.058 −0.063 0.111 0.145 0.160 0.049

All correlations are<0.7; n = 45.

Table S8. Mean trait values± SE of all measured species traits, separately for native and alien plant species Species traits Native species, mean± SE Alien species mean± SE n P Seed mass, g 2.93± 0.10 3.17± 0.13 93 0.16 Germination percentage, % 0.22± 0.04 0.52± 0.04 93 <0.0001 Relative growth rate, g g−1·d−1 _{0.10± 0.01 0.11± 0.01 67 0.61}

Shoot–root ratio 3.04± 0.59 5.64± 0.76 67 0.02

Response to shading, cm 0.38± 0.21 0.47± 0.06 55 0.61

Response to competition, g −1.66 ± 0.17 −1.87 ± 0.11 62 0.30

Herbivore resistance, g −0.37 ± 0.04 −0.35 ± 0.03 58 0.73